Female babies respond to pregnancy stress, male babies don’t

Being stressed is not good for a pregnant mother, but how the baby reacts to the stress depends partly on its gender. Research led by Vicki Clifton from the University of Adelaide is finding out how stress changes the way babies develop.

When you’re pregnant, I imagine anything can stress you out. Were I up the duff (which I am not), I would most certainly stress about demon possessions… I can’t help but think of Omen and the Ring.

But it’s not just the mind. Asthma attacks, smoking and pre-eclampsia can put pregnant bodies under stress. The mother can communicate that stress to the baby while it’s still in the womb. Cortisol, a molecule involved in stress, causes changes in the placenta – but only if the baby is female.

A female baby will slow her growth when her mother is stressed. How thoughtful! By growing slowly she takes less energy and nutrients from her mother, which the mother might need to recover.

In contrast, a male baby does not change his growth with a stressed mother. He just keeps growing as fast as he can.

At first glance, it seems like a smart move for the male baby. Mother is stressed, something might be wrong, better grow as fast as you can and get the hell outta there. Unfortunately it’s not a good option. If there’s a second stressful event, the male baby is at risk of pre-term delivery or dying in the uterus. A female baby who has curbed her growth has a better chance of surviving.

The Darwin obsessed among you might wonder what evolutionary advantage is made by females reacting better to stress. If you have any ideas let me know, because I’m stumped.

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Captain Skellett

I be Captain Skellett. Me blog started in April 2009 when I was working full time and didn’t get a chance to talk science. Now I have changed jobs and talk science all the time, but that doesn’t stop me blogging.
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I’m no fan of evo-woo explanaitons, but a good one I’ve heard for this is that female babies are more precious for passing on the next generation. If you have one male and five females you have five times as much baby potential as one female and five males. Female babies are more precious and need to therefore make extra sure that they actually come out safely.

Not sure how much i agree with that explanation but it does sort of work. My mother had pre-eclampsia during childbirth and according to the doctor both me (the little baby coming out) and her were stressing out like anything. They eventually had to knock us both out and do a cesarian we were that stressed.

As a scientist, I have read quite a bit of scientific literature concerning pre- and peri-natal reactions of male and female fetuses. Females of all ages are constitutionally stronger and more likely to survive many environmental insults. Male fetuses lose more neurons and faster than females during synapse pruning. Males develop schizophrenia about 5 years sooner, on average, than women do. Females survive cold temperatures much better than males do. Why? Nobody knows for sure. My speculation is that females underwent natural selection to make them strong enough to withstand multiple pregnancies, childbirth and child care throughout their adult lives. Men don’t do this. They take what they want (physically stronger and a violent nature) and until recently, never helped with childcare. Animals are not designed, they are constantly selected by their environments. Frail, unapdaptive fetuses and adults die or don’t procreate. Thanks to C-section and medical care, selection is now a whole lot less stringent. We may become like British and French bulldogs soon. Unable to birth naturally and a requirement for assisted insemination (Frenchies). Sorry guys.